Dendritic polymers (or “dendrimers”) have been used in the field of manufacturing protective coatings due to its unique structure which leads to the formation of high performance coatings. Protective coatings provide protection for a surface from damage by the elements such as water, snow, ice, heat, dirt, smog, bird droppings, chemical attacks and acid precipitation.
As dendritic polymers are polymers with hyperbranched structures which can comprise a high number of reactive functional groups exposed at the peripheral edges of the hyperbranched dendrimer molecule, they are considered as one of most promising resin systems to provide films with high cross-linking density and high surface protection performance. Depending on the degree of branching, dendritic polymers may be classified into first, second, third, fourth or even fifth generation dendritic polymers. A first generation dendritic polymer may theoretically have a total of eight peripheral reactive functional groups, whereas a second generation polymer will have theoretically sixteen peripheral functional groups, and whereas a third generation polymer will have theoretically thirty two peripheral functional groups and so forth. The total number of peripheral functional groups per molecule is also referred to as the peripheral functionality.
The molecules of dendritic polymers mimic the hydrodynamic volumes of spheres, and as such, they can be used to provide coatings of high molecular weights whilst maintaining relatively low viscosity. At the same time, dendritic polymers provide coatings with high crosslink density at the same time keep its flexibility.
Conventionally, protective coatings comprising dendritic polymers are provided as organic solvent-based coating systems due to the dendritic polymer's lack of solubility in water. Such solvent-based systems provide excellent abrasion resistance, flexibility, adhesion, and chemical resistance. However, due to the presence of organic solvents which are volatile in nature, coatings prepared from solvent-based systems will typically emit an undesirably high level of volatile organic compounds (“VOC”). in many countries have driven coating manufacturers to explore the possibilities of coating compositions having significantly reduced VOC emissions.
Further, another challenge for solvent-based coatings is to improve the solid content. One way to achieve this objective is to reduce the quantity of organic solvents so as to increase solid substances to obtain high solid coatings. However, lower solvent content will increase viscosity and sacrifice paint workability.
Additionally, dendritic polymers, especially high generation dendritic polymers, such as Boltorn H30™ and Boltorn H40™, are considered as a new class of macromolecular compounds, and are used in high performance coatings. However, these dendritic polymers typically possess melting points above 60° C. and require dissolution in organic solvents. While using organic solvents will improve the film forming properties for these dendritic polymer compositions, the trade-off is that solvent-based coatings may display inferior pencil hardness and chemical resistance if solvent is trapped in the highly cross-linked cured film and cannot be removed. The hazardous nature of organic solvents in a coating composition also limits the area of applications.
Accordingly, there is a need to provide a polymer composition that overcomes, or at least ameliorates, one or more of the disadvantages described above. In particular, it is an object of the present invention to provide a polymer composition that is capable of forming high performance coatings, with near-zero or zero VOC emissions and at the same time, display improved pencil hardness, chemical resistance relative to conventional solvent-based coatings.